Integrated electric motor driven compressor

ABSTRACT

A motor driven compressor assembly includes a motor housing having a fluid inlet and a fluid outlet. A motor is disposed within the motor housing and includes a rotor that is coupled to a rotatable shaft and a stator. Several passages fluidly connect the fluid inlet and the fluid outlet. One passage is located radially outward of the stator and another passage extends through the rotatable shaft. A compressor is in fluid communication with the fluid outlet of the motor housing. Operation of the compressor produces a fluid stream through the motor housing. The fluid stream transfers heat away from the motor to cool the motor.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/127,550, which was filed May 12, 2005.

BACKGROUND OF THE INVENTION

This invention relates to vacuum pumps and, more particularly, to amotor driven compressor assembly including a motor that is fluidlyconnected to a compressor.

Typical motor driven compressor assemblies include a reluctance motorfluidly connected to an inlet port of a screw compressor such that theoperation of the screw compressor evacuates an internal portion of thereluctance motor. The reluctance motor includes a rotor that rotatesrelative to a stator. The rotor is spaced apart from the stator suchthat air evacuated from the reluctance motor passes through the spacebetween the rotor and the stator. The compressor thereby produces a lowpressure within the internal portion of the reluctance motor. The rotorproduces less noise with lower air pressure, however, the low pressuremay produce a pressure drop at the inlet port of the compressor. As aresult of the pressure drop, the compressor may operate inefficiently orproduce an inconsistent vacuum.

Another problem with typical motor driven compressor assemblies is thatthe reluctance motor produces significant heat during operation. If theheat is not adequately removed, the reluctance motor may overheat whichmay result in a malfunction in the reluctance motor or the compressor.

Conventional motor driven compressors utilize air flow through the spacebetween the rotor and the stator to communicate heat away from thereluctance motor. Disadvantageously, the space is too small to flow asignificant quantity of air there through, which minimizes heatdissipation from the reluctance motor.

Accordingly, there is a need for a motor driven compressor assembly thatmore effectively cools the motor without a significant pressure drop atthe inlet of the compressor.

SUMMARY OF THE INVENTION

The motor driven compressor assembly according to the present inventionincludes a motor housing having an inlet and an outlet. The outlet isfluidly connected to a compressor such that the operation of thecompressor produces a fluid stream through the motor housing. The fluidstream through the motor housing communicates heat away from a motorwithin the motor housing to cool the motor.

Preferably, a shaft passage is located along a longitudinal axis of amotor shaft. A motor passage is located between a stator and a rotor ofthe motor. An outer passage is located radially outward from the stator,between the stator and the motor housing. The passages providesufficient space for fluid to flow through such that fluid streamingthrough the motor housing is not significantly restricted by thepassages.

Accordingly, the motor driven compressor assembly cools the motorwithout a significant pressure drop at the inlet of the compressor. Thisinvention addresses further provides enhanced capabilities whileavoiding the shortcomings and drawbacks of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows.

FIG. 1 is a schematic view of a vacuum system including a motor drivencompressor; and

FIG. 2 is a schematic view of the motor driven compressor of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates selected portions of an example vacuum system 10including a vacuum region 12, such as an industrial area that requires avacuum to move materials from one location to another. The vacuum region12 is fluidly connected to a suction line 14, which is fluidly connectedto a motor driven compressor 16. The motor driven compressor 16evacuates the vacuum region 12 through the suction line 14.

The motor driven compressor 16 includes a motor 18, preferably apermanent magnet motor, within a motor housing 20. The motor housing 20can be made from separate housing pieces as is illustrated, or from asingle integrated housing. The motor housing 20 includes an inlet 22fluidly connected to the suction line 14 and an outlet 24 fluidlyconnected to a compressor 26.

The motor 18 includes a stator 28 and a rotor 30 having permanentmagnets 31. A motor passage 33A extends between the stator 28 and therotor 30. The rotor 30 is connected to a shaft 32 that rotates about alongitudinal axis A. One section end of the shaft 32 is located in themotor housing 20 and another end of the shaft 32 is located in thecompressor 26. The shaft 32 includes a shaft passage 33B that extendsalong the longitudinal axis A through the shaft 32. The shaft passage33B includes an opening 35 that extends in a direction that istransverse to the longitudinal axis A at the outlet 24 of the motorhousing 20. The shaft passage 33B and opening 35 fluidly connect theinlet 22 of the motor housing 20 to the outlet 24.

Securing members 34 secure the motor 18 within the motor housing 20(FIG. 2). An outer passage 33C is provided between the motor housing 20and the stator 28. The outer passage 33C fluidly connects the inlet 22to the outlet 24 of the motor housing 20.

A fan 36 is coupled to the end of the shaft 32 within the motor housing20. A lock nut 37 or the like secures the fan 36 on the shaft 32 suchthat the fan 36 rotates with the shaft 32 to blow more fluid through thepassages 33A, 33B, and 33C. The fan 36 includes a suction side on theinlet 22 side of the fan 36 and a discharge side on the outlet 24 sideof the fan 36, as will be described below.

A valve assembly 38 is located between the motor 18 and the inlet 22within the motor housing 20. The valve assembly 38 includes a valvemember 40 in fluid communication with the inlet 22 and the suction line14. An actuator 42 moves the valve member 40 between open and closedpositions to control fluid flow through the valve assembly 38.

The outlet 24 of the motor housing 20 is fluidly connected to thecompressor 26. The compressor 26 includes a male compressor screw 50coupled to the shaft 32 for rotation with the shaft 32. A femalecompressor screw 52 is disposed in a meshing relationship with the malecompressor screw 50 for rotation with the first compressor screw 50.Operation of the male compressor screw 50 and the female compressorscrew 52 compresses fluid streaming into the compressor 26 from theoutlet 24. A compressor outlet 54 is fluidly connected to the compressor26 for discharge of compressed fluid.

During operation, the motor 18 is selectively activated to rotate therotor 30. The rotor 30 rotates the shaft 32 to rotate the first andsecond compressor screws 50 and 52. Rotation of the compressor screws 50and 52 compresses fluid within the compressor 26 and forces thecompressed fluid out of the compressor outlet 54. Discharge ofcompressed fluid from the compressor outlet 54 produces a suction at theoutlet 24 of the motor housing 20. The suctioning at the outlet 24produces a fluid stream from the vacuum region 12 through the suctionline 14, inlet 22, and motor housing 20.

When fluid enters the motor housing 20, the fluid streams from the inlet22 to the outlet 24 by way of at least one of the passages 33A, 33B, and33C (as depicted by arrows in FIG. 1). The stator 28, rotor 30, andshaft 32 transfer heat that is produced during operation of the motor 18to the fluid streaming through the passages 33A, 33B, and 33C. Thestreaming fluid transfers the heat to the motor housing 20, whichdissipates the heat to the surrounding environment. At least a portionof the streaming fluid, or carries the heat away from the stator 28,rotor 30, and shaft 32 through the compressor 26 to cool the motor 18.

The passages 33A, 33B, and 33C expose the streaming fluid to the stator28, rotor 30, and shaft 32 and to cool the motor 18 to an acceptableoperation temperature. Conventional motor driven compressor assembliesheretofore provided minimal exposure between a streaming fluid and themotor to significantly cool the motor. Preferably, the motor 18 is apermanent magnet motor, which generates less heat to dissipate and isgenerally smaller than some other types of motors such as inductancemotors such that a permanent magnet motor is preferred. Given thisdescription however, one of ordinary skill in the art will be able toadapt the disclosed examples for all types of motors and to meet theneeds of their particular application.

The passages 33A, 33B, and 33C provide sufficient space for fluid toflow through such that fluid streaming through the motor housing 20 isnot significantly restricted by the passages 33A, 33B, and 33C. That is,the passages are large enough to handle the stream of fluid withoutproducing a pressure build-up on the inlet 22 side or a pressure drop onthe outlet 24 side. This provides the benefit of a continuous andrelatively uniform supply of fluid to the compressor 26 without asignificant pressure drop at the outlet 24 of the motor housing 20. Itshould be understood that one of ordinary skill in the art with thebenefit of the teachings herein will be able to properly size thepassages to assure significant flow without a significant pressure drop

The valve assembly 38 selectively controls the fluid streaming inthrough the inlet 22. This provides the benefit of controlling themagnitude of suction produced within the vacuum region 12 and alsoallows control over the amount of fluid streaming through the motorhousing 20 to cool the motor 18.

The fan 36 further controls the magnitude of the suction. As is known,fans are generally designed to move fluids from a suction side to adischarge side of the fan. Rotation of the fan 36 produces additionalsuction at the inlet 22 side that draws more fluid through the inlet 22.The fan 36 also facilitates fluid flow from the motor housing 20 intothe compressor 26. On the outlet 24 side of the fan 36, the fan 36pushes fluid out of the motor housing 20 and into the compressor 26.This feature provides the benefit of increasing the rate of fluidstreaming through the motor housing 20 to increase cooling of the motor18. Additionally, the increase in the rate of fluid streaming throughthe motor housing 20 charges the compressor 26 with more fluid toincrease the efficiency of the compressor 26.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1. A method of cooling a motor driven compressor assembly, comprising:fluidly connecting a fluid outlet of a motor chamber and a fluid inletof a compressor; and operating the compressor to produce a fluid streamthrough the motor chamber to transfer heat from a motor within the motorchamber.
 2. The method as recited in claim 1, further comprising fluidlyconnecting a fluid inlet of the motor chamber to a passage, and fluidlyconnecting the passage to the fluid outlet of the motor chamber.
 3. Themethod as recited in claim 2, further comprising forming the passage atleast partially about a periphery of a stator of the motor.
 4. Themethod as recited in claim 3, further comprising forming the passage toinclude a radial dimension that varies along a circumference of thestator.
 5. The method as recited in claim 4, further comprising fluidlyconnecting the fluid inlet and the fluid outlet of the motor chamberwith another passage that extends through a shaft within the motor. 6.The method as recited in claim 2, further comprising forming the passagethrough a shaft within the motor.
 7. The method as recited in claim 1,further comprising moving a valve to control a flow rate of the fluidstream.
 8. The method as recited in claim 1, further comprising moving afan to control a flow rate of the fluid stream.
 9. A method of providinga cooling passage through a motor driven compressor assembly,comprising: eccentrically locating a motor within a cylindrical portionof a motor housing to thereby form a cooling passage between a stator ofthe motor and the motor housing.
 10. The method as recited in claim 9,further comprising operating a fan that is located upstream from thecompressor to influence a fluid stream through the cooling passage. 11.The method as recited in claim 9, further comprising mounting the motorwith mounting members that extend between the stator and the cylindricalportion of the motor housing.
 12. The method as recited in claim 9,further comprising dividing the cooling passage into sections.
 13. Themethod as recited in claim 9, further comprising mounting the motor atleast partially within the cylindrical portion such that a portion ofthe stator is in direct contact with the motor housing.
 14. A method ofcooling a motor driven compressor assembly, comprising: establishing afirst cooling passage that extends between a rotor and a stator of amotor; establishing a second cooling passage through a motor shaft ofthe motor; establishing a third cooling passage that extends between thestator and a motor housing that supports the motor; and operating thecompressor to produce a fluid stream through the first cooling passage,the second cooling passage, and the third cooling passage.
 15. Themethod as recited in claim 14, further comprising eccentrically locatingthe motor within a cylindrical portion of the motor housing to therebyform the third cooling passage.
 16. The method as recited in claim 14,further comprising operating a fan that is located upstream from thecompressor to influence the fluid stream.